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Mission

The mission, developed by the University of Arizona's Lunar and Planetary Laboratory, NASAGoddard Space Flight Center and Lockheed Martin Space Systems, is planned for launch in September 2016.[2] After traveling for approximately two years, the spacecraft will rendezvous with asteroid 101955 Bennu (1999 RQ36) in 2018, and begin 505 days of surface mapping at a distance of approximately 5 km (3.1 mi).[1] Results of that study will be used by the mission team to select the sample site and the gradual process of approaching, but not landing, and ultimately extending a robotic arm to gather the sample.[10]

An asteroid was chosen as the target of study because asteroids are a '[1]

Following collection (from 60 grams to 2 kilograms, or 2.1 oz to 4.4 lb), the sample will be returned to Earth in a capsule similar to that which returned the samples of comet 81P/Wild on the Stardust spacecraft. The return trip to Earth will be shorter, allowing the sample to return and land at the Utah Test and Training Range in 2023. The capsule will then be transported to the Johnson Space Center for processing in a dedicated research facility.[1]

Launch

Launch is planned for September 2016. On August 5, 2013, NASA announced OSIRIS-REx would launch on an Atlas V 411.[5] Interested persons were able to have their names inscribed on a microchip to be carried in the spacecraft. That open submission process for names is now closed. [11]

Science objectives

Samples will be returned to Earth in 2023

Telescopic observations have helped define the orbit of 101955 Bennu, a near-Earth object with a mean diameter in the range of 480 to 511 meters (1575 to 1678 ft).[12] It completes an orbit of the Sun every 436.604 days (1.2 years). This orbit takes it close to the Earth every six years. Although the orbit is reasonably well known, scientists continue to refine it. It is critical to know the orbit of Bennu because recent calculations produced a cumulative probability of 1 in 1410 (or 0.071%) of impact with Earth in the period 2169 to 2199.[13] Part of the OSIRIS-REx mission is to refine understanding of non-gravitational effects (such as the Yarkovsky effect) on this orbit, and the implications of those effects for Bennu's collision probability.

Telescopic observations have revealed some basic properties of 101955 Bennu. They indicate that 101955 Bennu is very dark and is classified as a B-type asteroid, a sub-type of the carbonaceous C-group asteroids. Such asteroids are considered "primitive", having undergone little geological change from their time of formation.

Specifications

The Sample Return Capsule (SRC) will be used for entering the Earth's atmosphere. The capsule with encased samples will be retrieved from Earth's surface and studied, as was done with the Stardust mission.

Payload

In addition to its telecommunication equipment, the spacecraft will carry a suite of instruments which will study the asteroid in many wavelengths,[16] as well as image the asteroid, and retrieve a physical sample to return to Earth.

OCAMS

The OSIRIS-REx Camera Suite (OCAMS) consists of the PolyCam, the MapCam, and the SamCam.[17] Together they acquire information on asteroid Bennu by providing global mapping, sample site reconnaissance and characterization, high-resolution imaging, and records of the sample acquisition.[18]

PolyCam, an 8-inch telescope, acquires images with increasingly higher resolution as the spacecraft approaches the asteroid.

MapCam searches for satellites and outgassing plumes. It maps the asteroid in 4 different colors, informs our model of asteroid shape and provides high resolution imaging of the sample-site.

SamCam continuously documents the sample acquisitions.

OLA

The OSIRIS-REx Laser Altimeter (OLA) is a scanning and LIDAR instrument that will provide high resolution topographical information throughout the entire mission.[19] The information received by OLA will create global topographic maps of Bennu, local maps of candidate sample sites, ranging in support of other instruments, and support navigation and gravity analyses.

OLA will scan the surface of Bennu at specific intervals in the mission to rapidly map out the entire surface of the asteroid to achieve its primary objective of producing local and global topographic maps. What OLA brings back about Bennu will also be used to develop a control network relative to the center of mass of the asteroid and enhance and refine gravitational studies of Bennu.

Goldstone radar-images of the asteroid formerly known as 1999 RQ36

OLA has a single common receiver and two complementary transmitter assemblies which enhance the resolution of the information brought back. OLA’s high-energy laser transmitter is used for ranging and mapping from 1 to 7.5 km. The low-energy transmitter is used for ranging and imaging at smaller distances (500 m to 1 km). The repetition rate of these transmitters sets the data acquisition rate of OLA. Laser pulses from both the low and high energy transmitters are directed onto a movable scanning mirror, which is co-aligned with the field of view of the receiver telescope limiting the effects of background solar radiation. Each pulse provides target range, azimuth, elevation, received intensity and a time-tag.

OTES provides full-disc Bennu spectral data, global spectral maps, and local sample site spectral information used to characterize the global, region, and local mineralogic composition and thermal emission from the asteroid surface. The wavelength range, spectral resolution, and radiometric performance are sufficient to resolve and identify the key vibrational absorption features of silicate, carbonate, sulfate, phosphate, oxide, and hydroxide minerals. OTES is also used to measure the total thermal emission from Bennu, which drives the requirement to measure emitted radiation globally. Based on the performance of Mini-TES in the dusty surface environment of Mars, OTES is resilient to extreme dust contamination on the optical elements.

REXIS

The Regolith X-ray Imaging Spectrometer (REXIS) will provide an X-ray map of Bennu, complementing core OSIRIS-REx mission science.[23] REXIS brings the strengths of four groups within Massachusetts Institute of Technology (MIT) and Harvard University utilizing the flight-proven Conceive, Design, Implement and Operate (CDIO) curriculum, with the potential to involve more than 100 students throughout the process. REXIS is based on flight heritage hardware, thereby minimizing elements of technical risk, schedule risk, and cost risk.

REXIS is a coded aperture soft X-ray (0.3–7.5 keV) telescope that images X-ray fluorescence line emission produced by the interaction of solar X-rays and the solar wind with the regolith of Bennu. Images are formed with 21 arcminute resolution (4.3 m spatial resolution at a distance of 700 m). Imaging is achieved by correlating the detected X-ray image with a 64 x 64 element random mask (1.536 mm pixels). REXIS will store each X-ray event data in order to maximize the data storage usage and to minimize the risk. The pixels will be addressed in 64 x 64 bins and the 0.3–7.5 keV range will be covered by 5 broad bands and 11 narrow line bands. A 24 s resolution time tag will be interleaved with the event data to account for Bennu rotation. Images will be reconstructed on the ground after downlink of the event list. Images are formed simultaneously in 16 energy bands centered on the dominant lines of abundant surface elements from O-K (0.5 keV) to Fe-Kß (7 keV) as well the representative continuum. During orbital phase 5B, a 21-day orbit 700 m from the surface of Bennu, a total of at least 133 events/asteroid pixel/energy band are expected under 2 keV; enough to obtain significant constraints on element abundances at scales larger than 10 m.

TAGSAM

The sample return system, called Touch-And-Go Sample Acquisition Mechanism (TAGSAM), consists of a sampler head with an articulated arm.[24] An on-board nitrogen source will support up to three separate sampling attempts for a minimum total amount of 60 g of sample. The surface contact pads will also collect fine-grained material.

Sampler head stored in Sample Return Capsule (SRC) and returned to Earth.

OSIRIS-REx 2

Phobos

OSIRIS-REx 2, if funded, would make it a double mission collecting samples from the two Mars moons for return to the Earth.[26] In a conference abstract in 2012, it was stated that this mission would be the both quickest and least expensive way to get samples from the moons.[27]

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